Practice Exam

1. (10 pts) The figure on the left illustrates the challenges to an environmental chemist. (a) Using acid rain as your illustration, discuss where as a result of a chemical reaction, SO2, the pollutant/contaminant can affect an ecosystem.

Challenge to the Environmental Chemist

Response Time

Pollutant/Contaminant

Environmental Effect(Chemical Rxs)

Organism Health

Increasing difficulty of linkage

Biochemical Effect(Biochemical Rxs)

Physiological Effect(Biological Response)

Ecosystem Effect

The points to emphasize here are (1) that SO2 itself is not a problem until it is oxidized to H2SO4 :

SO2 SO3 H2SO4 The acid will change the pH in aquatic systems resulting in fish kills, or affecting trees, particularly those at

high elevations in low-lying clouds.

(b ) Using indoor air, discuss briefly, how a pollutant/contaminant can affect human health (Any of the pollutants we discussed in class will be acceptable).

Whether you are talking about asbestos, smoke, or radon, some discussion of cancer. There are differences in how the pollutant causes the cancer whether radioactivity (radon) or physical fibers (asbestos).

(5 pts) Complete the table below that shows the atomic effects as a function of energy/wavelength

Region Atomic Effects

Microwave

Infrared

Visible

Ultra-violet

X-ray, -ray

(5 pts) Complete the table below that shows the atomic effects as a function of energy/wavelength

Region Atomic Effects

Microwave Rotation

Infrared Vibration

Visible Electronic excitation

Ultra-violet Bond-breaking

X-ray, -ray Bond-breaking

( 10 pts) List two concerns that have resulted from the destruction of the ozone layer in the stratosphere.

What I am looking for here is a discussion involving cataracts, skin cancer, or amphibian decline. Discussion must include an increasing of UV-B radiation as a result of ozone loss.

(15 pts) One of the compounds believed responsible for the destruction of the ozone layer, is CF2Cl2

Show a series of reactions beginning with the photolysis of CF2Cl2 that would result in the destruction of ozone (CF2Cl2 ---> CF2Cl + Cl).

O3 + Cl ClO + O2

ClO + O Cl + O2

List two sources of CFCs.

Refrigerants, cleaning solvents, blowing agents

Write a chemical reaction that could remove Cl from the stratosphere.CH4 + Cl HCl + CH3 or Cl + Cl Cl2

(15 pts) Explain what causes the ozone hole to appear and why it occurs in late October/early November (Be as specific as possible, using chemical reactions).

Earth turns – and Antarctic region gets cold and has no sunlight HNO3.3H2O precipitates out. HCl and ClONO2 undergo transformation to HOCl and Cl2 Earth turns, UV light appears, HOCl OCl + H or HO + Cl Also, Cl2 2 Cl Destruction begins. Earth Continues to turn: HNO3 melts, UV cleaves HNO3 and OCl

is taken out of the system

(10 pts) A compound, methyl bromide, CH3Br, used by regional strawberry farmers has been placed on a list to be eliminated by 2005 because of concern about ozone depletion. Please explain.

Concern about methyl bromide getting up into the stratosphere and causing the destruction of ozone.

CH3Br -- CH3 + Br

Br + O3 BrO + O2

BrO + O O2 + Br

(15 pts) The main compound responsible for acid rain is SO2 emission.

Explain why it is a problem down wind, and not in the immediate vicinity of where it is released.

SO2 is oxidized to H2SO4 and this is a slow oxidation-reduction reaction requiring time to occur, resulting in the sulfuric acid to be created a long distance from the source.

List two ways in which SO2 emission can reduced/eliminated. Conversion to another product (scrubber), dilution, or remove as

an impurity. List three effects resulting from acid rain. Vegetation, natural waters, health, or structure damage

(10 pts) One of the major regional concerns is nitrogen deposition as a result of the increasing swine population in SE North Carolina. Discuss this concern and how it can be abated, other than reducing the swine population.

Nitrogen deposition from the atmosphere resulting in a nutrient overload causing algal bloom and fish kills.

This effect can be mitigated by changing the lagoon system for treating the hog waste.

What conditions must exist for a city to have the potential problem of photochemical smog? Show, using chemical reactions, why we monitor the presence of ozone in the troposphere to indicate pollution.

Conditions for photochemical smog are:

Stagnant air NOx and VOCs High temperatures Sunlight

N2 + O2 ----> 2 NO(Combustion) 2 NO + O2 <--> NO2 (rev. rx. slow) NO2 -h<400 nm->NO+ O (UV-A, UV-B) [Sum of NO2 and NO given as NOx] O + O2 ---M---> O3

O3 ---h, <320 nm ---> O2* + O*

[Both in ground states or excited states, UV-B radiation is required to dissociate ozone into O*(excited state)]

O* + H2O -----> 2 OH {Must be in excited state to overcome repulsion}

How did you do?